Bags made of plastic film such as thin polyethylene film have been used in various sizes. Small bags are used in the packaging of sandwiches and the like; larger bags are used as grocery bags and even larger bags are used for containing trash. The present invention is particularly related to the large bags which are used to carry trash and garbage and where leakage is a problem.
U.S. Pat. No. 4,554,192-Benoit discloses the use of angle seals at the bottom corners of a thermoplastic grocery bag to relieve stress at the gusset point. The gusset point is where the gusset fold intersects the bottom seal of the bag. The gusset point is subject to much stress when the bag is loaded. Small holes emerging at the gusset points are a persistent problem in gusseted thermoplastic bags. Holes are a particular problem in bags used to carry garbage because even the smallest hole will cause leakage.
Diagonal bottom seals have been successfully used in grocery bags to reduce stress and prevent tearing and failure of loaded bags. Diagonal seals have also been used to provide a square bottom for thermoplastic bags as is shown in U.S. Pat. No. 3,857,329-Lehmacher; U.S. Pat. No. 3,660,959- La Fleur and in the British Patent 1,010,094-Crawshaw. These diagonal seals extend through two layers of film material, the front or rear bag panel and one of the gusset panels.
The use of such two-film angle seals has reduced tearing of grocery bags, but it has not eliminated the development of small holes at the gusset points in loaded bags. Such holes are prevalent in angle-sealed grocery bags. The development of these small holes is not a serious problem in grocery bags. However, leakage in a garbage bag is a significant problem.
It is an object of the present invention to prevent development of holes at the gusset points of thermoplastic bags so as to prevent leakage from such bags.